1. Field of the Invention
The invention relates to a power assist device for use in a luggage bin with a drop-down shell, in particular in a passenger aircraft with                a load measuring mechanism for determining the load acting on the drop-down shell of the luggage bin;        a power assist mechanism to apply an assist force to the shell counteracting the load where the power support mechanism has a mechanical spring whose end areas can move in an actuation direction toward one another against the return force of the spring from a first position into a second position and where a first end area of the spring can be supported by way of a first abutment point on a base section and a second end area of the spring can be supported by way of a second abutment point against a support element that can be connected to the shell;        an actuation mechanism set up to bring the power assist mechanism into an inactive operating state where moving the spring from the second position into the first position is blocked and an active operating state in which the spring can be moved from the second position into the first position;        where the load measuring mechanism has a control connection with the actuation mechanism such that the actuation mechanism is changed from the inactive operating state to the active operating state if the load determined by the load measuring mechanism exceeds a specified threshold that is greater than the assist force.        
2. Description of Related Art
Such a power assist device is known from DE 10 2006 045 189 B4. It has a luggage shell attached to a bracket. It is possible to pivot this shell from a lower, open position into the upper, closed position. So that the luggage shell can be pivoted by the user more easily from the open position into the closed position when carrying a heavier luggage load, the power assist device is equipped with a gas spring that can be brought into an active operating state and an inactive operating state.
In the active operating state, the gas spring is compressed while lowering the luggage shell from a first position corresponding to the closed position of the luggage shell into a second position corresponding to the open position of the luggage shell. In a corresponding manner, the gas spring expands from the first position into the second position when the luggage shell is pivoted from its lower, open position into its upper, closed position. During this process, the gas spring applies a constant assist force to the luggage shell that counteracts the luggage load acting on the shell and is less than this load.
If the load acting on the luggage bin drop-down shell is smaller than the assist force of the gas spring, the power assist mechanism is in the inactive operating state in which the luggage shell is pivoted from the lower, open position to the upper, closed position by the manual force of the user alone.
So that the operating state of the power assist device can automatically adapt to the load acting on the drop-down shell of the luggage bin, the power assist device has a load measuring mechanism that measures the load acting on the shell. The load measuring mechanism has a control connection with the actuation mechanism by way of an electronic control unit such that the actuation mechanism is changed from the inactive operating state to the active operating state when the load determined by the load measuring mechanism exceeds a specified threshold that is larger than the assist force and the luggage shell is in its lower, open position. In these circumstances, the open position of the luggage shell is detected using a touch sensor attached to one end stop, connected to the bracket, with which the luggage shell makes contact in the open position. To switch from the active operating state to the inactive operating state, a stepper motor driven by means of the control system closes a valve located in the gas spring and this valve blocks the gas spring in its second, compressed position corresponding to the open position of the luggage shell.
The previously known power assist device, however, has the disadvantage that, in the event of a fault in the electronic control system and/or in the touch sensor, it may occur that the valve of the gas spring actuates when the luggage shell is not in the open position. In this case, the luggage shell is blocked in the position in question, a situation that may result in it no longer being possible to open the luggage bin to remove the luggage inside.
As a result, the task is to create a power assist device of the type described above in which blocking of the drop-down shell in the closed position and/or an intermediate position between closed and open is reliably avoided.